Recently, a network called an OpenFlow is attracting the attention (see Patent Literature 1 and Non Patent Literatures 1, 2). The OpenFlow uses a centralized control type network architecture in which a control apparatus termed an OpenFlow controller controls the behavior of a switch termed an OpenFlow switch. With the OpenFlow, it is possible to flexibly modify the behavior of switches, together making up a virtual network, in keeping with the status of the network in its entirety. Thus, with the use of the OpenFlow, a virtual network high in flexibility can be constructed with much ease.
On the other hand, a network management system (NMS) or a policy server is used in a network system in order to exercise monistic control over security, service quality or otherwise in a network system.
In Patent Literature 2, there is disclosed a management computer that generates the port setting information (paragraphs 0043, 0044 and 0062). The port setting information provides for the information on whether or not each port provided in each switch is to carry out the client authentication function based on the setting policy and the network configuring information. This setting policy provides for a switch or a port which does not automatically set whether client authentication is to be performed. In the Patent Literature, it is stated that the management computer generates the configuration definition based on the port setting information 1140 and causes it to be reflected in the switch as necessary (see paragraphs 0029 and 0063).
In Patent Literature 3, there is disclosed a policy management system including a polling means and a trap means, configured for monitoring the network, and a policy application instruction means, configured for correcting the policy as necessary. In Patent Literature 4, there is disclosed a quarantine network system which enlarges the possible accessing range stepwise as security check goes on.    [PATENT LITERATURE 1]    Japanese Patent Kokai Publication No. JP-P2011-170718A    [PATENT LITERATURE 2]    Japanese Patent Kokai Publication No. JP-P2008-060692A    [PATENT LITERATURE 3]    Japanese Patent Kokai Publication No. JP-P2004-236030A    [PATENT LITERATURE 4]    Japanese Patent Kokai Publication No. JP-P2010-287932A    [NON-PATENT LITERATURE 1]    Nick McKeown and seven others, “OpenFlow: Enabling Innovation in Campus Networks”, [online], [retrieved Heisei24 (2012) February 14], Internet <URL: http://www.openflow.org/documents/openflow-wp-latest.pdf>    [NON-PATENT LITERATURE 2]    “OpenFlow Switch Specification” Version 1.1.0 Implemented (Wire Protocol 0x02), [online], [retrieved Heisei24 (2012) February 14], Internet <URL: http://www.openflow.org/documents/openflow-spec-v1.1.0pdf>